This invention relates to a filing guide, and more particularly to a filing guide useable in connection with saw chain which facilitates filing of parts of the chain for the purpose of maintaining the cutting performance of the chain.
The usual cutter link in saw chain includes a body portion at the base of the link provided with rivet holes useable in connecting the link to other saw chain links. Integral with this body portion at the forward end of the cutter link is an upwardly projecting depth gauge and integral with the body portion at the rear end of the link and separated from the depth gauge by a gullet is an upwardly projecting cutter formed by a side plate which joins with the body portion and a top plate. Periodically, cutting edges at the forward extremity of the cutter provided along leading edge portions of the side plate and top plate must be filed to sharpen the cutter, and this filing must be performed in a precise manner if the cutter link is to cut properly. Furthermore, after the cutter in the cutter link is filed away with use, the height of the depth gauge should be reduced, to maintain proper clearance between the top of the depth gauge and the cutting edge in the top plate of the cutter. Additionally, in so-called safety chain constructed for anti-kickback characteristics, a side link in the chain on the opposite side of the chain from the cutter link may be provided which has an upward projection disposed laterally of and in the vicinity of the depth gauge which functions to limit penetration of the cutter. This projection, too, optimally should be filed periodically to maintain a proper relation between the height of this projection, the height of the depth gauge and the height of the cutting edge at the leading end of the cutter.
Various types of filing guides have been proposed in the past. Most have been rather cumbersome, and as a corollary expensive, which has detracted from wide spread use, and use by chain saw operators in the field where it is impractical to carry such devices around. Plate-type filing guides have also been proposed, and while these have performed satisfactorily in connection with the filing of certain types of chain, they have not lent themselves for use with certain newly developed safety chains which include safety links with upper expanses functioning to inhibit kickback.
A general object of this invention is to provide an improved filing guide useable in the filing of cutter links in saw chain which is simple and easily carried, and permits a person of only ordinary skill precisely to file operating parts of cutter links in a saw chain, as well as anti-kickback safety projections which may be included in the chain.
The filing guide of the invention takes the form of a plate having a flat expanse, and means forming an elongate shoulder extending transversely of the plate at the forward end of the plate. This shoulder serves to elevate the forward end of the guide to set the proper angle for the expanse in the plate extending rearwardly from the shoulder-forming means.
As contemplated by a preferred embodiment of the invention, the guide may be inverted by turning the guide side edge over side edge. The shoulder-forming means above referred to takes the form of a cylindrical expanse extending transversely of the guide, with one side of this cylindrical expanse projecting outwardly from one face of the flat expanse in the plate and the other side of the cylindrical expanse projecting outwardly from the opposite face of the flat expanse in the guide. With the guide positioned so that one face of the flat expanse faces downwardly, the cylindrical expanse mentioned serves to elevate the forward margin of the guide, with the guide inclining upwardly from where so elevated and in position to facilitate the filing of a depth gauge and a safety projection. Turned over, the cylindrical expanse elevates the forward margin of the guide with the flat expanse of the guide inclining downwardly from this forward margin and at a proper angle to facilitate the filing of a cutter in a cutter link.